| Abstract: | This study is concerned with fiber structure of new high‐modulus type PBO fiber. Crystal modulus and molecular orientation change with stress was surveyed. Standard‐modulus type PBO (AS) fiber has hysteresis effect to applied stress while high‐modulus type PBO (HM) fiber shows reversible change. In order to raise actual PBO fiber modulus higher, nonaqueous coagulation process was adopted with conventional heat treatment. The fiber (HM+) so made gives 360 GPa in the Young's modulus and an absence of small‐angle X‐ray scattering pattern that is characteristic for aqueous‐coagulated PBO fiber with heat treatment (Zylon™ HM). The crystal structure form and crystal size for the HM+ fiber are the same as those of the HM fiber. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1605–1611, 2000 |
